The present invention relates to a device and methods for dividing a multiphase flow into several flows which has substantially the same mixture of phases.
When oil and or gas are produced from subsea wells, the produced fluid is often a multiphase mixture. There may also be a need for treating this multiphase mixture flow, for instance cooling it before it is separated into the different substances as gas, oil, water, sand or other fluids following the multiphase flow. When for instance cooling a flow it is favorable to have smaller amounts to be cooled to ensure the necessary cooling and then it would be favorable to split the multiphase flow into several mainly equal smaller flows.
Proper distribution of such a multiphase flow is challenging. The flow composition may differ between the outlets in a splitting point and in the extreme one outlet may contain only gas or liquid. For subsea systems it is for several reasons necessary to have control of the splitting between parallel flow lines, process systems or process equipment; 1) for equal loading; 2) for assurance of sufficient inhibited liquid.
A solution for systems with small liquid volume flow compared to gas volume flow has been especially challenging. The challenge concerns equal distribution of liquid and gas in general. This application is important if MEG is present in a gas-condensate system and need to be equally distributed into several pipes to avoid hydrate formation. It can also be important if equal loading of flow rates into two or more lines is required.
There are some known solutions for providing splitting of a multiphase flow into several flow paths. U.S. Pat. No. 4,293,025 describes a flow splitter using a tank having an inlet and two outlets where the outlets are configured as vertical standpipes extending partway into the tank. The fluids enter into the tank from the top and are prevented from directly entering into the standpipes by baffles. Liquid gathers at the bottom of the tank. The standpipes in this system are perforated such that the liquid enters the standpipes through the perforations while vapour enters into the standpipes from the top. This device is used for distributing a liquid-vapour mixture for a heat exchanger. In U.S. Pat. No. 7,261,120 there is shown a similar arrangement but here the standpipes are located at the top end of the tank and projecting downwards into the tank while the inlet is located at the bottom. The standpipes in this system are also perforated. U.S. Pat. No. 4,662,391 describes a flow splitter for liquid-vapour mixtures which is basically in the shape of a four-way piping hub. The hub has an inlet and a bottom drain directly opposite the inlet and two outlets perpendicular to the inlet. Fluid will collect in the central chamber of the hub. When the liquid accumulates to the point where it reaches the edge of the side outlets the liquid divides equally among the two outlets to become re-entrained with a substantially equal portion of the vapour passing through each outlet. The drain is used to regulate the height of the fluid in the central chamber.
None of these solutions gives a satisfying solution for splitting a multiphase flow especially when the use of the equipment is subsea. An aim with the present invention is therefore to provide an alternative device and method for obtaining a splitting of a multiphase flow to several smaller flows which has mainly equal content when looking at the different fluids in the flow.